1. Field of the Invention
The present invention relates to a rotary compressor which is provided with a driving element and first and second rotary compression elements driven by a rotation shaft of this driving element, the elements being disposed in a sealed container, and in which a refrigerant compressed by the first rotary compression element is compressed by the second rotary compression element to send the refrigerant into the sealed container.
2. Description of the Related Art
Heretofore, in this type of rotary compressor, for example, a high inner pressure type rotary compressor, a rotation shaft is of a vertically disposed type. The compressor includes: a driving element; a first rotary compression element driven by the rotation shaft of this driving element; and a second rotary compression element whose displacement volume is smaller than that of the first rotary compression element, the elements being disposed in a sealed container. The first and second rotary compression elements are constituted of: upper and lower cylinders constituting the first and second rotary compression elements, respectively; rollers fitted into eccentric portions disposed on the rotation shaft to eccentrically rotate in the respective cylinders; an intermediate partition plate disposed between the respective cylinders to close an opening of one of the opposite cylinders; and a support member which closes the other opening of each cylinder and which includes a bearing of the rotation shaft. The face of each support member on a side opposite to each cylinder is depressed, and this depressed portion is closed with a cover to thereby form a discharge noise absorbing chamber.
Moreover, when the driving element is driven, the rollers fitted into the eccentric portions disposed integrally with the rotation shaft eccentrically rotate in the upper and lower cylinders. Accordingly, a refrigerant gas is sucked from a suction port of the first rotary compression element into the cylinder on a low-pressure chamber side. The gas is compressed by operations of the roller and a vane to obtain an intermediate pressure. The gas is discharged from the cylinder on a high-pressure chamber side to the discharge noise absorbing chamber via a discharge port. Thereafter, the intermediate-pressure refrigerant gas discharged to the discharge noise absorbing chamber is sucked from the suction port of the second rotary compression element into the cylinder on the low-pressure chamber side. Then, the gas is compressed by the operation of the roller and vane in a second stage to form a high-temperature high-pressure refrigerant gas, and the gas is discharged from the high-pressure chamber side into the sealed container via the discharge port and the discharge noise absorbing chamber. Accordingly, the inside of the sealed container has high temperature and pressure. On the other hand, the refrigerant gas sent into the sealed container is discharged from a refrigerant discharge tube to the outside of the rotary compressor (see, e.g., Japanese Patent Application Laid-Open No. 2004-27970).
In such multistage compression type rotary compressor, a thickness (dimension in a roller diametric direction) of each roller is set so that a displacement volume of the first rotary compression element as a first stage is larger than that of the second rotary compression element as a second stage. That is, heretofore, the upper and lower cylinders having equal inner diameters (bore diameter) and heights, and the opposite eccentric portions having equal diameters are used with respect to the first and second rotary compression elements. The thickness of the first roller is set to be smaller than that of the second roller so that the displacement volume of the first rotary compression element becomes larger than that of the second rotary compression element.
However, the high inner pressure type rotary compressor has a large pressure difference between the cylinder of the first rotary compression element and the sealed container. In a case where the thickness of the roller of the first rotary compression element is reduced to reduce a sealing width by the roller, a problem occurs that the refrigerant leaks from a roller end face.
Especially, a gap between the intermediate partition plate and the rotation shaft has a high pressure in the same manner as in the inside of the sealed container. Therefore, this high pressure easily flows from the roller end face into the cylinder. When the thickness of the roller of the first rotary compression element is reduced, the inflow of such high pressure increases, and a volume efficiency of the first rotary compression element disadvantageously deteriorates.